1. Field of the Invention
The present invention relates to a rotation transmission member in which a resin gear is molded by insert molding on the external surface of one end of a gear section formed almost over the entire length of a metal insert member. It also relates to a method of manufacturing the rotation transmission member.
2. Discussion of the Related Art
Automotive parts often use resin gear sections for rotation transmission at parts of a rotation transmission device. Such resin gear sections are useful because they can damp rotation vibration in a rotation transmission train to enhance quietness. Generally, a resin gear section is bodily joined by resin molding or the like with the external surface of a cylindrical metal member, wherein it is required that the resin gear section does not fall or come off the metal member even when loads act on the resin gear section in the circumferential direction as well as in the axial direction.
To this end, in the prior art described in, e.g., Japanese Unexamined, Published Patent Application No. 2003-21223, a part of resin material is filled in cutouts or holes formed on a metal part (metal member) at the time of the injection molding of the resin gear section, so that the resin gear section can be prevented from falling or coming off the metal member even when loads act on the resin gear section in the circumferential direction as well as in the axial direction.
Because the technology described in the aforementioned prior art is of the method that a part of resin material is filled in the cutouts or holes formed on the metal part (metal member) at the time of the injection molding of the resin gear section, there arises a problem that the technology cannot be utilized for a rotation transmission member which does not have any cutout or hole on the metal part.
For this reason, it may be conceived that as shown in FIG. 7, a shape machining section 4 such as knurling or serration is machined on an insert portion 3 of a metal member 2 which section is to have a resin gear section 1 resin-molded thereon, to prevent the resin gear section 1 and the metal member 2 from falling or coming off each other.
However, where the metal member 2 constitutes a gear section 5 for rotation transmission as is the case of FIG. 7, it becomes necessary to machine the gear section 5 for rotation transmission and the shape machining section (knurling or serration) 4 for coming-off prevention separately on the external surface of the metal member 2. These are distinctive machinings, thereby increasing in machining steps as well as in part cost.